This invention relates to a semiconductor device, or more in particular to a structure of a semiconductor rectifier.
The required specifications of a semiconductor device vary with the intended applications thereof. In particular, high reliability in the resistance to thermal fatigue and vibrations is required for a semiconductor rectifier or the like used for rectification in an AC generator for an automobile, which comprises heat-radiating plates making up anode electrodes (or cathode electrodes), semiconductor elements soldered to the heat-radiating plates, and header leads soldered onto the semiconductor elements and functioning as cathode electrodes (or anode electrodes), the header leads being connected to lead terminals electrically and mechanically. While an automobile engine is running, the output current of the AC generator changes with engine revolutions independently of whether the automobile is running or stationary. At the same time, the heat generated in the semiconductor device and the temperature within the engine room undergo a change, while the semiconductor device is subjected to vibrations. As a result of these temperature changes, the component parts constituting the semiconductor device are subjected to expansion and contraction. Further, since vibrations occur along the length of the header leads and also in the lateral directions thereof, the resulting stress is repeatedly applied to the solder interposed between the semiconductor elements and the header leads, often causing the breakdown of the solder due to thermal fatigue.